1. Technical Field of the Invention
The present invention relates to the field of electronics, and more particularly, to an improved large-area parking-monitoring system, e.g. a city-wide parking-monitoring system.
2. Prior Arts
Locating a vacant parking space causes much frustration to motorists. It increases fuel consumption and has a negative impact to the environment. To conserve energy resources and enhance the quality of the environment, it is highly desired to develop a parking-monitoring system, which can transmit substantially real-time parking occupancy data to motorists. Based on the parking occupancy data, a motorist can be guided towards a vacant parking space at destination.
Many parking-monitoring systems disclosed in prior arts are designed for a small parking area (e.g. a parking lot or few city blocks), not for a city spanning a few square kilometers. To monitor parking city-wide, U.S. Patent Application 61/757,627 filed by Zhang on Jan. 28, 2013 discloses a large-area parking-monitoring system. This system comprises a plurality of parking-monitoring devices. Each device monitors a large number of parking spaces and transmits parking occupancy data through a cellular network. This data transmission is characterized by a small amount of data per transmission (e.g. as little as a few bytes) and long intervals (e.g. one transmission every minute). Considering that a city-wide parking-monitoring system comprises hundreds to thousands of parking-monitoring devices, if all of them transmit parking occupancy data with the above characteristics through the cellular network, a lot of cellular resource will be wasted.